Silver (Ag) film has wide applications in micro-electromechanical system such as reference electrode, interconnect and inductance. The majority of Ag metallisation patterning is realised by dry technology, which is inefficient and high cost. Electroplating process using negative photoresist SU-8 as the electroplating mould has been reported for Ag film patterning. However, the UV solidified SU-8 is difficult to remove. An acid cyanide-free Ag plating bath (thiosulphate bath) has been introduced to fabricate patterned Ag film using the positive photoresist as the electroplating mould, which is environment-friendly and compatible with the micro-electromechanical systems process. The Ag film with different line widths was fabricated by micromachining process. Compared to the reported bath, the Ag film presented here had smaller roughness, crystallites and higher hardness, which would improve its performance. A low cost, efficient and environment-friendly method to fabricate thick patterned Ag film, which had potential applications in electronic industry and medical apparatus, was provided.

An ultrathin-channel trench single gate tunnelling field-effect transistor (trench SG-TFET) with a 5 nm channel thickness is proposed and investigated. Trench SG-TFETs demonstrate a higher I _ON (∼8 times), a steeper sub-threshold swing (SS) (average SS of 46.2 mV/decade and point SS of 21.8 mV/decade), and a higher I _ON/I _OFF current ratio (∼10 times) as compared with the conventional SG-TFET at V _DS = 0.4 V and temperature of 300 K. Also by using intrinsic region in drain, it has a strong immunity to short-channel effects in extremely scaled trench SG-TFETs. The proposed trench SG-TFET seems to be attractive for future energy-efficient circuit applications.

The performance and electrical characteristics of hybrid carbon nanotube field effect transistor (CNTFET) are studied. Hybrid CNTFET consists of heavily doped carbon nanotube (CNT) as a one contact connected to intrinsic CNT as a channel. The opposite side of the channel is connected to a metal as the other contact. If the source is the metal and the drain is the heavily doped, this type is called metal–semiconductor hybrid CNT or MSH-CNTFET. While when the source is the heavily doped and the drain is the metal, this is called semiconductor–metal hybrid CNT or SMH-CNTFET. The electrical characteristics of the device has been studied using a two-dimensional (2D) quantum mechanical simulator by solving 2D Poisson's equation self consistently with Non-equilibrium Green function (NEGF). The proposed devices are found to overcome the ambipolar conduction of Schottky barrier CNTFETs and improve frequency performance of metal–oxide–semiconductor CNTFETs.

The Cu@BaTiO₃ powders were synthesised by a simple low-cost hydrothermal method for the very first time. The effects of copper (Cu) contents on the formation of core(Cu)@shell(BaTiO₃) powders have been investigated by X-ray powder diffraction, scanning electron microscopy and energy dispersive spectrometer. Notably, the existence of Cu@BaTiO₃ powders can only be obtained when Cu content happened to be 20%. A novel modification method, gaseous rare-earth penetration, has been adopted to reduce the resistivity and prepare Cu@BaTiO₃ conductive powders. The results indicated that rare-earth penetration turned out an effective way to lower the resistivity of Cu@BaTiO₃ powders significantly. Surprisingly, the core–shell structure of Cu@BaTiO₃ powders has not perished after rare-earth penetration. Furthermore, the resistivity of Cu@BaTiO₃ conductive powders turned out to be 8.30 × 10⁻⁴ Ω m, which can be a promising candidate for novel and environmental-friendly conductive powders.

Potential of luminescent bacteria in production of metal nanoparticles (NPs) has not been well evaluated up until now. These bacteria contain lux operon which is included of reductase enzymes, by increasing bacterial cell density, the expression of aldehyde synthetic enzymes elevate and enhance the yields of NPs synthesis. Therefore, extracellular synthesis of gold NPs (AuNPs) using natural occurring luminescent bacteria, VLA, VLB, VLC and genetically engineered luminescent bacteria, Pseudomonas putida KT2440 and Pseudomonas fluorescence OS8 have been successfully conducted. NPs were characterised and their antibacterial activity evaluated using microtitre plates at different concentrations against some hospital pathogenic bacteria. Biosynthetic AuNPs produced had maximum absorption at the ranges of 500–550 nanometre wavelengths. Transmission electron microscopy images showed particle sizes between 10 and 50 nanometres and confirmed the success of purification process. The NPs were spherical and the FTIR analysis showed the existence of biomolecules on surface of purified NPs that could be most probably related to reductase enzymes that are stabilised on NPs surfaces. Further investigation on antibacterial properties of these novel NPs which coated by reductase enzymes showed that any increase or decrease in antibacterial activity is dependent on NPs concentration.

It is found that propylene carbonate (PC)-based nano-fluids (NFs) exhibit substantially larger breakdown voltages and higher breakdown stabilities than that of pure PC when they contain various nano-particles with different conductivity and permittivity. However, both the fast electron scavenging model and the potential well model fail to explain these experimental phenomena rationally. It is proposed that the interaction region between nano-particles and PC will create myriad trap sites and capture electric charge carriers effectively. Therefore, the trapped and accumulated homo-charges can weaken the electric field intensity, increase the charge injection barrier height and reduce further charge injection in the vicinity of electrodes. This is the main physical mechanism for the enhanced dielectric performances of PC-based NFs.

Porous ZnMnO₃ plates have been prepared by an initial formation of Zn/Mn–sucrose composite and subsequent calcination route. The influences of calcination temperatures on the structures and electrochemical performances of target ZnMnO₃ are clearly studied. At an optimal calcination temperature of 500°C, the ZnMnO₃ composed of numerous nanoparticles possesses an obvious plate-like structure and porous property, and a Brunauer–Emmett–Teller specific surface area of ∼25.50 m² g⁻¹ and average pore size of ∼19.69 nm can be reached. As lithium-ion battery anode, the optimal ZnMnO₃ delivers a reversible (second) discharge capacity of 709.6 mAh g⁻¹ at 0.4 A g⁻¹. After 100 cycles, a discharge capacity of 560.0 mAh g⁻¹ can be retained. Even at a high current density of 1.2 A g⁻¹, the sample still shows a discharge capacity of 403.1 mAh g⁻¹. The good electrochemical performance of as-prepared ZnMnO₃ may be attributed to its unique porous structure.

Nanofluid fuels, a new class of nanotechnology-based fluids, are liquid fuels with a stable suspension of nanometre-sized particles. The preparation of fuel mixtures and achieving to a stable and long-term suspension is the key step in nanofluid synthesis. The idea of this work is to suspend nano- and micron-sized boron particles in kerosene, exploring the differences between the complete sedimentation times of particles in fuel at various weight fractions of surfactants and investigating the viscosity of nanofluid at low weight concentration of nanoparticles. Various surfactants including oleic acid, propylene glycol, sorbitan oleate, Tween 85 and CTAB were used to prepare stable kerosene/boron slurries. Suspensions were prepared with varying surfactant loadings of 0.1–2.0% by weight, in steps, for the same particle loading of 0.5 wt%. The results showed that sorbitan oleate was the best surfactant and the optimum weight ratio of boron particle to sorbitan oleate for enhanced stability of nanofluid was determined to be 2. The complete sedimentation time of nanoparticles at the most stable nanofluid was ∼57 h. At low temperature and high weight fraction of particles, nanofluids showed similar 67% enhancement in viscosity properties.

A novel high DC and radio-frequency (RF) characteristics AlGaN/GaN metal insulator semiconductor high electron mobility transistor (MIS-HEMT) with a high-K/low-K compound gate dielectric layer (CGD) is proposed. Owing to the different dielectric constants, the discontinuity of the electric field at the high-K/low-K interface can modulate the distribution of the electric field along the channel under gate. Hence, enhancement of DC and RF characteristics can be achieved. The optimised results of the AlGaN/GaN MIS-HEMT with CGD structure revealed that the DC transconductance g_m and the maximum saturation current I_ds increased about 10.5 and 6.9% compared with the traditional AlGaN/GaN MIS-HEMT with single high-K gate dielectric layer (SGD), respectively. Also, the cutoff frequency f_t and the maximum oscillation frequency f _max of 74.2 GHz and 129.2 GHz are obtained and improved about 18.5 and 14.7% compared with the device with SGD structure.

Under different nanomagnets’ size, switching behaviour of all spin logic (ASL) devices constructed with Co and permalloy (Py) nanomagnets are studied by using the coupled spin-transport/magneto-dynamics model. The results indicate that ASL devices’ switching delay and energy dissipation can be reduced by decreasing the thickness of nanomagnets. The switching delay and energy dissipation of PyASL are lower than those of CoASL in a smaller thickness of nanomagnet, but they increase much faster than those of CoASL when the nanomagnets (FM) thickness increases. With the dimensional scaling of nanomagnets, the ASL devices’ switching delay and energy dissipation decrease rapidly and the influence of thermal noise become weak. Moreover, under the same nanomagnet volume, ASL devices’ switching delay, energy dissipation, and energy barrier can be reduced by decreasing aspect ratio. These findings can provide guidelines for optimising the ASL devices’ materials and size.

Developing a rapid and easy approach to fabricate crystalline silk fibroin nanofibres without any needs for post-processing stage is focused. Thus, methanol bath was chosen as the collector and then the effect of soaking time on the properties of fibroin fibres was investigated. The results indicated that the wet-electrospun mats had higher fibre diameter than mats made by conventional electrospinning system. With prolonging the electrospinning time in methanol bath, a slight increase in the average fibre diameter and crystallinity were observed. In addition, the stiffness of the wet-electrospun mats increased with increasing soaking time, while the breaking stress decreased. The cellular viability of the osteoblast-like cells (MG63) on fibroin mats improved during wet-electrospinning process, while no significant difference was observed for cell attachment. Accordingly, it seems that wet electrospinning in methanol for 30 min is optimal for bone regeneration on account of viability and mechanical property.

A novel approach to the design and fabrication of field-emission tips with self-aligned gates intended for electric propulsion micro-thruster applications is presented. Their micro-electromechanical systems fabrication process is derived from the recent proliferation of research toward developing field emitter arrays, which are used primarily for field-emission flat-panel display applications. An array of micron-sized tips for electric field enhancement via wet isotropic etching of silicon, using silicon nitride as a hard mask is fabricated. The wet etching is accomplished using a combination of hydrofluoric, nitric, and acetic acids. The tips were then coated with a metal layer to enhance wetting by indium, the proposed propellant. Next, a layer of SU-8 photoresist was applied by spin coating and patterned to serve as a dielectric spacer. A second layer of metal was then applied to serve as a gate electrode. In addition, the results of electrostatic simulations of the prototype is described.

Conventional methods for measuring contact angle are usually applied on smooth surfaces. Methods concerning contact angle determinations performed directly on pore surfaces of porous media have rarely been reported. This work approaches the pore-scale measurement of local contact angle in a CO₂–brine–glass beads system, using micro-focused X-ray computed tomography (micro-CT). Both drainage and imbibition experiments with 0.1 ml/min injection rate were conducted at 40°C and 8 MPa. The effectiveness of this pore-scale approach is confirmed by comparing the results with the results gathered from traditional sessile drop methodology. Observations indicate that the contact angle hysteresis phenomenon was not so obvious for intermediate-wet glass beads in the employed experimental setting. In real reservoir circumstances, the roughness and capillary variation caused significant deviations in contact angle distribution for both drainage and imbibition, even in rock cores consisting of a single-phase material.

Parallel plate actuators (PPAs) are widely used in micro-electro-mechanical systems. Control strategies for PPAs often require displacement and velocity feedback that may be measured with various sensing techniques, which may require additional structures or distort the steady-state behaviour. An alternative approach of designing an estimator using the measured voltage across the PPA without additional sensing structures and distortions is proposed in this work. This novel method can improve the performance and reduce the device's footprint with full-state (displacement and velocity) feedback information, using a series resistor. A system model using this configuration is investigated. The observability of this self-sensing technique is analysed using a small signal model. Then, a singular value decomposition is applied to examine how to further improve the observability by choosing appropriate parameters. Simulation and numerical studies were performed which validate this method.

Spherical silica particles with uniform size (90–520 nm) were successfully fabricated using Stöber method. The size of silica particle (fabricated from ethanol, water, ammonia and tetraethyl orthosilicate) was examined by field-emission scanning electron microscopy. The effect of stirring rates (0–1200 rpm), reaction temperatures (12–75°C) and total volumes (80–400 0ml) on silica particle size was studied in detail. The experiment results indicate that stirring rates has no significant impact on the average size of silica particles, while higher temperature and larger total volume of reactant both result in smaller silica particles.

Nanostructured zinc oxide (ZnO) with different morphology has been synthesised by a facile hydrothermal method combining calcination procedure at different temperatures. The effect of calcination temperature on the morphology and electrochemical properties of as-synthesised ZnO is investigated. X-ray diffraction, scanning electron microscopy and transmission electron microscopy were applied to characterise the phase composition and microstructure of the synthesised samples. The electrochemical tests of as-synthesised ZnO as an anode material for lithium ion batteries (LIBs) reveal that ZnO nanoparticles prepared at 700°C deliver the largest capacity of 1815.8 mAh g⁻¹, while cabbage-like ZnO nanosheets prepared at lower temperatures display better cycling stability. It is believed that the diverse morphologies of nanostructured ZnO crucially affect their electrochemical properties as an anode material for LIBs.

To improve the degradation efficiency of TiO₂ for low concentrations of volatile organic compounds, TiO₂ loaded on activated carbon fibres (ACF) was prepared by an impregnation–hydrothermal method. The crystal structure, surface area, dispersion, optical absorption properties, and chemical composition of the TiO₂/ACF composite materials were characterised by X-ray diffraction, Brunauer−Emmett−Teller analysis, scanning electron microscopy, ultraviolet–visible absorption spectroscopy, and X-ray photoelectron spectroscopy. The influence of the hydrothermal temperature, illumination time, space velocity, and light intensity on the photocatalytic activities of the TiO₂/ACF composite materials was investigated with toluene as a model pollutant. The results showed that the phase of TiO₂ was anatase, which was dispersed as a thin film on the ACF surface. The crystallinity, dispersion, UV absorption, and hydroxyl group content of TiO₂ increased with an increase of hydrothermal temperature, whereas the photocatalytic activity of TiO₂/ACF was maximised when the hydrothermal temperature was 180°C. Increases in illumination time, space velocity, and light intensity were beneficial for regeneration of the composite materials. However, the energy efficiency decreased with increased light intensity. The degradation efficiency of toluene reached 40% with reaction conditions of illumination time: 3 h, space velocity: 1400 h⁻¹, and light intensity: 32 W. This degradation efficiency decreased 3.3% after recycling five times.

Thin-film Au electrodes prepared by magnetron sputtering method were used to develop a potentiometric CO₂ gas sensor. The thermal evaporated Li₃PO₄ played the role of electrolyte and sensing material. This design can simplify the fabrication process compared with the conventional solid electrolyte potentiometric CO₂ sensor (c-sensor) and improve the performance compared with the thick-film Au electrodes sensor (t-sensor). The designed CO₂ sensor (d-sensor) presented good response characteristics at the CO₂ concentration range of 250–2500 ppm and the electromotive force (EMF), ΔEMF/dec, response and recovery time were investigated. The EMF values of the sensor were linearly dependent on logarithm of CO₂ partial pressure at the working temperatures between 420°C and 500°C. The d-sensor showed a sensitivity of 79.1–93.7 mV/dec at working temperatures range of 420–500°C which was much higher than the sensitivities of c-sensor and the t-sensor. The response and recovery time of the fabricated sensors were 10 and 14 s at working temperature of 500°C, respectively. The surface morphology of Au thin films was considered to increase the three-phase interface area and be good for the reaction gases to diffuse from Au film to lithium phosphate, allowing rapid chemical reaction equilibrium, getting a more stable EMF output.

Low toxic, non-stoichiometric colloidal copper–indium–sulphur [Cu–In–S (CIS)] ternary quantum dots with different Cu:In molar ratios by a hot-injection method in octadecene was synthesised. The Cu:In precursor molar ratios were 1/10, 1/20 and 1/40. Varying the fraction of cationic and capping agents, the compositions of CIS nanocrystals were precisely controlled. The photoluminescence (PL) results reveal that, reducing the Cu:In ratio in the CIS is the feasible strategy for bandgap engineering. Tunable PL emissions have been observed. X-ray powder diffraction and high-resolution transmission electron microscopy results indicate that as-prepared CIS nanocrystals are compositional homogeneity. The single-crystal nature of CIS nanocrystals improves the relative PL quantum yield up to 12%, which exhibits substantial enhancement comparing with the stoichiometric CuInS₂ and CIS-based semiconductor core QDs. The PL decay curve of CIS has a triexponential feature. The value of τ1, τ2 and τ3 of CIS sample agree well with CuInS₂ core QDs. The average PL lifetime of CIS is reduced to 146.9 ns, which can be attributed to the reduction of surface-related trap states.

Porous microspheres capable of delivering high payloads of biomolecules with suitable biodegradability and biocompatibility would be valuable in delivery systems to aid tissue regeneration. In this work, a facile and scalable technique was induced to prepare poly(L-lactic acid) (PLLA) porous microspheres by combining an oil-in-oil surfactant-free phase inversion emulsion with thermally induced phase separation method. The morphology and property of the microspheres were investigated by scanning electron microscopy and N₂ adsorption test. Comparing to the conventional biodegradable microspheres, the nanoscale topographic structured PLLA microspheres may find wide applications in biomedical fields.